When performing an ANSI electroacoustical analysis, the hearing instrument must be _____________.

The correct answer pertains to the requirement that the hearing instrument must be placed in "test mode" during ANSI (American National Standards Institute) electroacoustical analysis. When a hearing aid is in test mode, it disables certain user-specific settings that may alter the performance of the device. This allows for accurate measurements of the hearing aid's electroacoustic performance as per standardized protocols.

In this mode, the device functions under uniform conditions, ensuring consistency and reliability in testing by providing a controlled environment for measurements such as gain, output, frequency response, and distortion. This standardization is crucial for comparing the performance of different hearing aids and for ensuring compliance with regulatory and safety standards.

The other choices do not ensure the integrity of the testing process as effectively as placing the device in test mode. For instance, positioning the hearing aid in situ means testing it as it would typically be worn, which may introduce variables that can affect the results. Setting the instrument to the wearer's default setting or connecting it to programming software could also interfere with obtaining accurate readings, as these actions do not isolate the performance of the hearing aid in a standard testing environment.